Powder paints containing particulate metal I

ABSTRACT

Metal particles used as color producing component in powder coating compositions are individually encapsulated in a thin and continuous coating of thermosettable, organic film-former prior to mixing with the particulate, organic, material which serves as the principal film-former of the powder coating composition. The coated particles are prepared by spray drying a solution of a controlled amount of the thermosettable material in a volatile solvent in which the metal has been dispersed. In the preferred embodiment, the coating thus achieved on the metal particles is cross-linkable with the principal film-former of the powder coating composition.

RELATION TO PARENT APPLICATION

This application is a Continuation-in-Part of copending U.S. Pat.application Ser. No. 422,472, filed Dec. 6, 1973 under the same titleand now abandoned. This application contains the illustrative examplesof the parent application and additional illustrative examples whereinthe amounts of thermosettable film-forming material deposited on themetal particles prior to their incorporation into a power paint areabove that illustrated in the parent. The recitational disclosures as tothe same in the body of the specification are conformed to take intoaccount the additional examples.

BACKGROUND OF THE INVENTION

One basic technique for the manufacture of powder coating materials isthe so-called fusion method. This involves the mixing of solvent-freeraw materials in their molten state, usually via some form of extruder,cooling, pulverization and size separation-classification. This methodhas a number of disadvantages unrelated to pigmentation and anadditional short-coming when metal flakes are employed as pigments. Thehigh shear employed in the mixing storage results in deformation of themetal flakes. Additionally, during the pulverization step, the metalflakes are further deformed and reduced in particle size. Coatingsproduced from such powders are characterized by a low level ofbrilliance and poor polychromatic appearance.

Another basic technique for the manufacture of powder coating materialsis the so-called solution-preparation, solvent-separation techniquewhich can be effected by more than one method. This general techniqueinvolves the preparation of a coating material in an organic solvent,separation of the solvent from the paint solids, and size-separationclassification. Also, pulverization in some form may or may not berequired depending upon the solvent separation method involved.

The separation of the solvent can be carried out by conventional spraydrying techniques or by heat exchange separation wherein the componentsof a paint solution are separated by volatilization of the more volatilesolvent and separation of the volatilized solvent from thenonvolatilized paint solids by gravitational forces. Since the metalflakes can be added after pulverization, if pulverization is requiredwhen using any of the solvent separation methods, damage to the metalflakes during pulverization can be avoided by using the solutionpreparation-solvent-separation technique. Problems do arise, however,with respect to distribution and orientation of the metal flakes whenthe powder coating material is applied to the substrate to be coated.This is particularly true when the method of application is that ofelectrostatic spray, the method most commonly employed to apply thefinal coating of paint to automobiles and a variety of other metalmanufacturers. In such applications, the flakes tend to orient in arandom fashion with a low percentage of the flakes parallel to thesubstrate. The net result is a high degree of metal protusion withlittle metallic brilliance and a low gloss factor.

Thus, when either of the aforedescribed methods are used to producemetal-pigmented, powder-paint coatings in accordance with the prior artprocesses, a substantially higher aluminum to non-metal pigment ratio isrequired, relative to the same ratio in liquid paints, in order toachieve the same degree of brightness and metallic appearance obtainedwith liquid paints. Further, the problem of metal flakes protusionremains even when brightness and metallic appearance are achieved.

In liquid paints, it is known to partially coat aluminum flakes used aspigments to increase the electrostatic spray efficiency of such paints.In U.S. Pat. No. 3,575,900, a method is disclosed for precipitating theresin of the solution coating upon the aluminum flake in colloidal form.This solution is then used as such or mixed with another solution foruse. The patentee specifically points out that, while it may beconvenient to call this encapsulation, it is not intended to denote thatthe aluminum particles are completely enveloped. This resin disclosedfor this purpose is a copolymer of vinyl chloride and monethylenicallyunsaturated monomers containing about 60 to about 90 percent weightvinyl chloride. Aluminum flake is also partially coated in U.S. Pat. No.3,532,662. Here the coating was carried out with a random copolymer ofmethyl methacrylate and methacrylic acid absorbed on the pigment. Bythis method, a dispersion is made of the solid particles in a liquidcontinuous phase comprising an organic liquid containing in solution apolymer which is absorbed by the particles and a stabilizer, andmodifying the polarity of the continuous phase so that the polymer isinsoluble therein, the stabilizer being a compound container an anchorcomponent which becomes associated with the absorbed polymer on theparticle surface and a pendant chain-like component which is solvated bythe modified continuous phase and provides a stabilizing sheath aroundthe particles. It is alleged that this improves the "wetting" of thetreated particles by the film-forming material dispersion-type coatingcomposition.

Powder paints have certain advantages over conventional liquid paints inthat they are essentially free of volatile solvents but they alsopresent problems which differ from the problems encountered with liquidpaints. These differences include differences with respect to employmentof aluminum flakes as a color producing component. For instance, whenflakes partially coated by resin precipitate are employed in liquidpaints, there remains the organic solvent and other components of thesolution to prevent direct exposure of the flake to the atmosphere andother external influences. Further, in powder paints, if aluminum flakeis coated, the coating must be a relatively dry solid and the size,weight and continuity of the organic encapsulation are all factors inaffecting the distribution of such particles when electrostaticallysprayed with the powder that is the principal film-former of the coatingcomposition.

THE INVENTION

This invention is concerned with the preparation, use and composition ofpowder paints containing metal particles, particularly aluminum flakes,and, in most applications, at least one non-metal color producingcomponent. The "non-metal color producing component" may be a particularpigment, dye or tint and may be either organic, e.g., carbon black, orinorganic, e.g., a metal salt.

In the practice of this invention, metal particles which areincorporated in powder paints to provide the metallic color component ofa monochromatic or polychromatic finish are encapsulated in athermosettable, organic coating through which the metal particle isvisible to the human eye. This coating which is preferably transparent,but may be translucent, allows a substantial percent of the metal flakesto be oriented parallel to the substrate even when the powder coatingmaterial is applied to the substrate by conventional electrostatic spraypainting.

The term "substantially transparent" is used herein to means materialswhich are either transparent or translucent or partially transparent andpartially translucent.

In accordance with this invention, the coated metal particles areadmixed, i.e., cold blended, with the balance of the coating materialafter the principal film-former is in particulate form. The non-metalcolor producing component may be admixed with the film-forming powderbefore, after or during the addition of the coated metal particles butsuch component is preferably added before the coated metal particles.This order of mixing avoids degradation of the metal particles in any ofthe steps of preparing the film-forming powder.

The metal particles most often used as a metallic color producingcomponent are aluminum flakes. To avoid unnecessary complication of thedescription of this invention, aluminum flakes will be used toillustrate the invention. If should be understood, however, that thismethod is applicable to any particulate metal used as a color producingcomponent in a powder coating material. This includes particles whichare solely metal, metal coated organic particles and polymer-sandwichedmetal particles having exposed metal edges.

The film-former used to coat the metal particles in accordance with thisinvention may be the same as or different than the principal film-formerof the powder coating material. The film-former used to coat the metalparticles in an organic, thermosetting, film-former which may take theform of a self-crosslinkable polymer or a chemically-functional polymerand a crosslinking agent reactable therewith. In the preferredembodiment, it is also crosslinkable with the principal film-former ofthe powder coating composition.

The preferred method for coating the aluminum flakes is to disperse theflakes, preferably in the form of aluminum paste, in a small amount ofthermosetting organic film-former and a solvent for the film-former thatis suitable for spray drying. The dispersion is then spray dried byconventional spray drying techniques. Since there is a small amount offilm-former relative to the amount of metal flakes, the net result is ametal flake coated with a relatively thin, continuous, coating of thefilm-former as opposed to a metal flake imbedded in a relatively largeparticle of the film-former.

More specifically, one first disperses the aluminum flakes in about 2 toabout 200 weight percent of thermosettable film-former, based on theactual weight of aluminum flakes, i.e., about 2 to about 200 parts byweight of thermosettable film-former per 100 parts by weight aluminumflakes. In one embodiment wherein the coating of such flakes isrelatively light, the aluminum flakes are dispersed in about 2 to about30 weight percent of thermosettable film-former based on the actualweight of the aluminum flakes, i.e., about 2 to about 30 parts by weightof thermosettable film-former per 100 parts by weight aluminum flakes.In most applications, it will be found advantageous to use between 10and 200, preferably between about 30 and about 70, parts by weight ofthermosettable film-former per 100 parts by weight aluminum flakes. Whenmetal particles of different density are used, the weight of aluminumflakes of the same surface area can be used to determine the amount offilm-former to use in coating the metal particles. When less that about2 weight percent of the film-former is used, complete encapsulation ofthe metal flakes may not result. When more than about 30 weight percentof the film-former is used, care must be taken in controlling the spraydrying operation to minimize the formation of an excessive amount ofspherical particles containing more than one metal flake. The incidenceof full coverage is high in the 30 to 70 range above described. Suchspherical particles can be removed from the other coated aluminum flakesby screening. The inclusion of large, multileafed particles in a curedcoating provides an irregular appearance. A similar result may beobtained if one mixes the uncoated metal flakes with the principalfilm-former of a powder paint while the latter is in liquid state andthen removes the solvent.

Aluminum paste is aluminum flakes, usually about 60 to about 70 weightpercent, in a smaller amount, usually about 30 to about 40 weightpercent, of a liquid hydrocarbon solvent which serves as a lubricant,e.g., mineral spirits. A small amount of an additional lubricant, e.g.,stearic acid, may be added during the milling operation which producesthe aluminum flakes. Everett J. Hall is credited with originating themethod of beating aluminum into fine flakes with polished steel balls ina rotating mill while the flakes are wet with a liquid hydrocarbon. SeeU.S. Pat. No. 1,569,484 (1926). A detailed description of aluminumpaste, its manufacture, flake size, testing, uses in paint, etc. isfound in Aluminum Paint and Powder, J. D. Edwards and Robert I. Wray,3rd Ed. (1955), Library of Congress Catalog Card Number: 55-6623,Reinhold Publishing Corporation, 430 Park Avenue, New York, New York,U.S.A. and the same is incorporated herein by reference.

The film-former used to coat the aluminum flakes may be aself-crosslinking polymer or copolymer or a chemically functionalpolymer or copolymer and a monomeric crosslinking agent. The preferredfilm-formers for this purpose include thermosettable copolymer systemscomprising: (a) an epoxy-functional copolymer of monovinyl monomers andas crosslinking agent therefor a C₄ - C₂₀, saturated, straight chain,aliphatic, dicarboxylic acid crosslinking agent-exemplified by U.S. Pat.application Ser. No. 172,236 filed Aug. 16, 1971, now U.S. Pat. No.3,752,870: (b) an epoxy-functional copolymer of monovinyl monomers andas crosslinking agent therefor a mixture of about 90 to 98 percent byequivalent weight of a C₄ - C₂₀, saturated, straight chain, aliphaticdicarboxylic acid and about 10 to about 2 percent by equivalent weightof a C₁₀ - C₂₂, saturated straight chain, aliphatic, monocarboxylicacid-exemplified by U.S. Pat. No. 3,730,930; (c) an epoxy-functionalcopolymer of monovinyl monomers and as crosslinking agent therefor adiphenol having a molecular weight in the range of about 110 to about550 - exemplified by U.S. Pat. application Ser. No. 172,228 filed Aug.16, 1971, now U.S. Pat. No. 3,758,634; (d) an epoxy-functional copolymerof monovinyl monomers and as crosslinking agent therefor a carboxyterminated polymer-exemplified by U.S. Pat. application Ser. No. 172,229filed Aug. 16, 1971, now U.S. Pat. No. 3,781,380; (e) anepoxy-functional copolymer of monovinyl monomers and as crosslinkingagent a phenolic hydroxy terminated polymer - exemplified by U.S. Pat.application Ser. No. 172,225 filed Aug. 16, 1971, now U.S. Pat. No.3,787,520; (f) an epoxy-functional, carboxy-functional,self-crosslinkable copolymer of ethylenically unsaturated monomers -exemplified by U.S. Pat. application Ser. No. 172,238 filed Aug. 16,1971, now U.S. Pat. No. 3,770,848; (g) a hydroxy-functional,carboxy-functional copolymer of monoethylenically unsaturated monomers -exemplified by U.S. Pat. application Ser. No. 172,237 filed Aug. 16,1971, now U.S. Pat. No. 3,787,340; (h) an epoxy-functional copolymer ofmonovinyl monomers and as crosslinking agent therefor an anhydride of adicarboxylic acid - exemplified by U.S. Pat. application Ser. No.172,224 filed Aug. 16, 1971, now U.S. Pat. No. 3,781,379; (i) ahydroxy-functional copolymer of monoethylenically unsaturated monomersand as crosslinking agent therefor a compound selected from dicarboxylicacids, melamines, and anhydrides - exemplified by U.S. Pat. applicationSer. No. 172,223 filed Aug. 16, 1971 and abandoned in favor orcontinuation application Ser. No. 407,128 filed Oct. 17, 1973 in turnabandoned in favor of continuation-in-part application Ser. No. 526,547filed Nov. 25, 1974; (j) an epoxy-functional copolymer of monovinylmonomers and as crosslinking agent therefor a compound containingtertiary nitrogen atoms - exemplified by U.S. Pat. application Ser. No.172,222 filed Aug. 16, 1971, now U.S. Pat. No. 3,758,635; (k) acopolymer of an alpha-beta unsaturated carboxylic acid and anethylenically unsaturated compound and as crosslinking agent therefor anepoxy resin having two or more epoxy groups per molecule - asexemplified by U.S. Pat. application Ser. No. 172,226 filed Aug. 16,1971, now U.S. Pat. No. 3,758,633; (l) a self-crosslinkable,epoxy-functional, anhydride-functional copolymer of olefinicallyunsaturated monomers - exemplified by U.S. Pat. application Ser. No.172,235 filed Aug. 16, 1971, now U.S. Pat. No. 3,758,632; (m) anepoxy-functional copolymer of monovinyl monomers and as crosslinkingagent therefor a carboxy terminated polymer, e.g., a carboxy terminatedpolymer, e.g., a carboxy terminated polyester, - exemplified byapplication Ser. No. 223,746 filed Feb. 4, 1972 and abandoned in favorof continuation-in-part application Ser. No. 489,271 filed Aug. 5, 1971;(n) an epoxy-functional copolymer of vinyl monomers and as crosslinkingagent therefor a dicarboxylic acid - exemplified by U.S. Pat.application Ser. No. 228,262 filed Feb. 22, 1972, now U.S. Pat. No.3,787,521; (o) an epoxy-functional and hydroxy-functional copolymer ofmonovinyl monomers and as crosslinking agent therefor a C₄ - C.sub. 20,saturated, straight chain, aliphatic dicarboxylic acid - exemplified byU.S. Pat. application Ser. No. 394,874 filed Sept. 6, 1973 and abandonedin favor of continuation-in-part application Ser. No. 552,676 filed Feb.24, 1975; (p) an epoxy-functional copolymer of monovinyl monomers withoptional hydroxy and/or amide functionality and as crosslinking agenttherefore (1) a C₄ - C₂₀, saturated, straight chain, aliphaticdicarboxylic acid and (2) a polyanhydride - exemplified by U.S. Pat.application Ser. No. 344,881 filed Sept. 6, 1973 and now abandoned infavor of continuation-in-part application Ser. No. 552,556 andcontinuation-in-part application Ser. No. 552,557 both filed Feb. 24,1975; (q) an epoxy-functional amide-functional copolymer of monovinylmonomers and as crosslinking agent therefor an anhydride of adicarboxylic acid - exemplified by U.S. Pat. application Ser. No.394,880 filed Sept. 6, 1973 and now abandoned in favor ofcontinuation-in-part application Ser. No. 552,572 filed Feb. 24, 1975;(r) an epoxy-functional, hydroxy-functional copolymer of monovinylmonomers and as crosslinking agent therefore an anhydride of adicarboxylic acid - exemplified by U.S. Pat. application Ser. No.394,879 filed Sept. 6, 1973 and now abandoned in favor of applicationSer. No. 552,511 filed Feb. 24, 1975; (s) an epoxy-functional,amide-functional copolymer of monovinyl monomers and as crosslinkingagent therefore a carboxy-terminated polymer - exemplified by U.S. Pat.application Ser. No. 394,875 filed Sept. 6, 1973 and now abandoned infavor of continuation-in-part application Ser. No. 552,518 filed Feb.24, 1975; (t) an epoxy-functional copolymer of monovinyl monomers and ascrosslinking agent therefore a monomeric or polymeric anhydride and ahydroxy carboxylic acid - exemplified by U.S. Pat. application Ser. No.394,878 filed Sept. 6, 1973 and now abandoned in favor ofcontinuation-in-part application Ser. No. 552,079 filed Feb. 24, 1975;(u) an epoxy-functional, amide-functional copolymer of monovinylmonomers and as crosslinking agent therefore a monomeric or polymericanhydride and a hydroxy carboxylic acid - exemplified by U.S. Pat.application Ser. No. 394,877 filed Sept. 6, 1973 and now abandoned infavor of continuation-in-part application Ser. No. 552,078 filed Feb.24, 1975; and (v) an epoxy-functional hydroxy-functional copolymer ofmonovinyl monomers and as crosslinking agent therefore a monomeric orpolymeric anhydride and a hydroxy carboxylic acid - exemplified in U.S.Pat. application Ser. No. 394,876 filed Sept. 6, 1973 and now abandonedin favor of continuation-in-part application Ser. No. 552,077 filed Feb.24, 1975.

The disclosures of the aforementioned patents and patent applicationsare incorporated herein by reference.

The term "vinyl monomer" as used herein means a monomeric compoundhaving in its molecular structure the functional group ##EQU1## whereinX is a hydrogen atom or a methyl group.

Other thermoset film-formers suitable for use in coating the metalparticles include, but not by way of limitation thermosettable systemsin which the polymeric component is a polyester, a polyepoxide andurethane-modified polyesters, polyepoxides and acrylics. As with theacrylics heretofore more specifically described, these may beself-crosslinking polymers or may be a combination of functional polymerand a coreactable monomeric compound which serves as crosslinking agent.

The preferred thermosettable powder paints known to applicants forautomotive topcoats, the use wherein metallic pigments find theirgreatest use, consist essentially of an epoxy-functional copolymer ofolefinically unsaturated monomers and a crosslinking agent therefor.Such paints, exclusive of pigments, may also contain flow controlagents, catalysts, etc. in very small quantities.

The copolymer referred to in the preceding paragraph has averagemolecular weight (M_(n)) in the range of about 1500 to about 15,000 andglass transition temperature in the range of about 40°C. to about 90°C.The epoxy functionality is provided by employing a glycidyl ester of amonoethylenically unsaturated carboxylic acid, e.g., glycidyl acrylateor glycidyl methacrylate, as a constituent monomer of the copolymer.This monomer should comprise about 5 to about 20 weight percent of thetotal. Additional functionality, e.g, hydroxy functionality or amidefunctionality, may also be employed by inclusion of a C₅ - C₇ hydroxyacrylate or methacrylate, e.g., hydroxyethyl acrylate, hydroxyethylmethacrylate, hydroxypropyl acrylate, or hydroxy-propyl methacrylate, orin alpha-beta olefinically unsaturated amide, e.g., acrylamide ormethacrylamide, among the constitutent monomers. When such additionalfunctionality is used, the monomers providing it comprise about 2 toabout 10 weight percent of the constituent monomers. The balance of thecopolymer, i.e., about 70 to about 93 weight percent of the constituentmonomers, are made up of a monofunctional, olefinically unsaturatedmonomers, i.e., the sole functionality being ethylenic unsaturation.These monofunctional, olefinically unsaturated monomers are, at least inmajor proportion, i.e., in excess of 50 weight percent of theconstituent monomers, acrylic monomers. The preferred monofunctionalacrylic monomers for this purpose are esters of C₁ - C₈ monohydricalcohols and acrylic or methacrylic acid, e.g., methyl methacrylate,ethyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate,hexyl acrylate and 2-ethylhexyl acrylate. In this preferred embodiment,the remainder, if any, aside from the aforementioned epoxy, hydroxy andamide functional monomers which also have olefinic unsaturationfunctionality used up in the polymerization formation of the copolymer,is preferably made up to C₈ - C₁₂ monovinyl hydrocarbons, e.g., styrene,vinyl toluene, alpha methyl styrene and tertiary butyl styrene. Othervinyl monomers which are suitable in minor amounts, i.e., between 0 and30 weight percent of the constituent monomers, include vinyl chloride,acrylonitrile, methacrylonitrile, and vinyl acetate.

The crosslinking agents employed with the aforedescribed copolymer willhave functionality that will react with the functionality of thecopolymer. Thus, all of the crosslinking agents heretofore mentioned inthe recital of powder paint patents and patent applications, e.g., C₄ -C₂₀ saturated, aliphatic dicarboxylic acids, mixtures of C₄ - C₂₀saturated aliphatic dicarboxylic acids and monocarboxylic acids ofcarbon number in the same range, carboxy terminated copolymers havingmolecular weight (M_(n)) in the range of 650 to 3000, monomericanhydrides preferably anhydrides having a melting point in the range ofabout 35° to 140°C., e.g., phthalic anhydride, maleic anhydride,cyclohexane-1,2-dicarboxylic anhydride, succinic anhydride, etc.,homopolymers of monomeric anhydrides, and mixtures of such anhydridesand hydroxy acids having a melting point in the range of 40° to 150°C.,are suitable for use as crosslinking agents for these copolymers. Thedisclosures of all patents and patent applications recited herein areincorporated herein by reference. In general, these crosslinking agentsare employed in amounts such as to provide between about 0.3 and about1.5, preferably between about 0.8 and about 1.2, functional groups whichare reactable with functional groups on the copolymer per functionalgroup on the copolymer.

The best acrylic, thermoplastic, powder coatings known to applicants arecopolymers of alpha-beta olefinically unsaturated monomers. These aremade up either solely or predominantly of acrylic monomers, i.e.,acrylates, methacrylates, mixtures of acrylates and methacrylates and asmall fraction of acrylic or methacrylic acid. In the embodiment whereinthe copolymer is made up predominantly of acrylic monomers, i.e., inexcess of 51 weight percent acrylic monomers, the acrylic monomers mayinclude up to about 5 weight percent acrylic acid, methacrylic acid or amixture of acrylic and methacrylic acids while the balance is made up ofC₈ - C₁₂ monovinyl hydrocarbons, e.g., styrene, vinyl toluene, alphamethyl styrene, and tertiary butyl styrene. The acrylates andmethacrylates used in either of these embodiments are preferably estersof a C₁ - C₈ monohydric alcohol and acrylic acid or methacrylic acid ora mixture of acrylic and methacrylic acids. Thus, such a copolymer wouldcontain about 46 to about 100 weight percent of esters of a C₁ - C₈monohydric alcohol and acrylic or methacrylic acid, 0 to about 49 weightpercent of C₈ - C₁₂ monovinyl hydrocarbons and 0 to about 5 weightpercent acrylic or methacrylic acid with the sum of the aforementionedesters and acrylic or methacrylic acid comprising in excess of 51 weightpercent of the comonomers as stated earlier in this paragraph. One suchcopolymer contains about 76 to about 81 mole percent methyl methacrylate1 to 3 mole percent acrylic acid or methacrylic acid or a mixture ofacrylic and methacrylic acids, and 16 to 23 percent butyl methacrylate.

"Alpha-beta unsaturation" as used herein includes both the olefinicunsaturation that is between two carbon atoms which are in the alpha andbeta positions relative to an activating group such as a carboxyl group,e.g., the olefinic unsaturation of maleic anhydride, and the olefinicunsaturation between the two carbon atoms which are in the alpha andbeta positions with respect to the terminus of an aliphaticcarbon-to-carbon chain, e.g., the olefinic unsaturation of acrylic acid,methyl methacrylate or styrene.

DETAILED DESCRIPTION OF THE INVENTION

The preparation of the coated metal flakes is carried out in a solventfor the film-former that is sufficiently volatile for efficient spraydrying and which will not chemically react with either the film-formerof the metal flakes to a degree that will significantly modify theirproperties or appearance within the contact times employed to carry outthe spray drying process. A preferred solvent for this purpose ismethylene chloride. Other solvents which can be used include toluene,xylene, methyl ethyl ketone, acetone and low boiling petroleum naphthas.

A typical formulation for the feed stock for the spray drier inaccordance with this invention would include the following:

                     Parts by Weight                                              ______________________________________                                        aluminum paste     30.00                                                      film former        2.00                                                       MeCl.sub.2         200.00                                                     ______________________________________                                    

Typical operating parameters for a convention, 3 ft. diameter spraydrier equipped with a conventional two-fluid nozzle atomizer, e.g., aglass and a liquid as in a convention air stomixing (liquid) paint spraygun are as follows:

    air flow          197 cubic feet/minute                                       feed flow         380 ml/min.                                                 inlet air temperature                                                                           180°F.                                               outlet air tempera-                                                            ture              80°F.                                               product rate       6 lbs./hr.                                             

The coated aluminum, as received from the spray drier, is then sievedthrough a screen of desired particulate size, e.g., a 44 micron screen,to remove excessively large particles. Approximately 20 percent of theproduct in the form of oversize particles is discarded.

The non-metal powder component, hereinafter called the "powdercomponent" comprises the primary film-forming component and, where thefinish is to be polychromatic, at least one metal color producingcomponent. This non-metal color producing component may be a pigment,dye or tint. For purposes of this invention, white and black shall beconsidered colors inasmuch as a light reflecting or light absorbingmaterial must be added to the organic film-former to provide the finishwith a white or black appearance in the same manner that a material mustbe added to the organic film-former which reflects light rays thatconvey to the eye one color while absorbing others.

The film-forming component of the powder component is preferably athermosetting film-forming material. Those thermosetting film-formingmaterials heretofore disclosed for use in coating the metal leaves aresuitable for use as the principal film-former of the powder component.The thermosets preferred for the coating of the metal leaves are alsothe preferred thermosets for this purpose.

In addition, the principal film-former of the powder component of thisinvention may be a thermoplastic powder, e.g., a thermoplastic acrylicpolymer having a molecular weight (M_(n)) in the range of 30,000 to80,000 and a glass transition temperature in the range of 60°C. to110°C. - as exemplified by U.S. Pat. application Ser. No. 172,227 filedAug. 16, 1971. These coated flakes, of course, can be used with anythermoplastic powder suitable for use as the principal film-former ofany thermoplastic powder paint.

The formulation of the non-metal powder component, which in the case ofa polychromatic finish contains a non-metal color producing component,is prepared taking into consideration the particular color chosen foremployment with the metallic color component and the amount of themetallic color component to be employed. The powder component isquantitatively formulated taking into account the amount of material tobe brought in through the addition of the coated metal particles.

A typical composition for the powder component is as follows:

                      Parts by Weight                                             ______________________________________                                        film-former         94.33                                                     flow control additive                                                                             0.67                                                      pigment             5.00                                                      ______________________________________                                    

The preparation and processing of the non-metal powder component intopowder form is carried out by one of the conventional powder preparationtechniques, e.g., extrusion, spray drying, or solvent extraction. Oncein powdered form, this material is sieved through a suitable screen,e.g., a 74 micron screen.

The final step in the preparation of the powder coating material of thisinvention is the blending of the two major components, i.e., thethermoset, organic coated particulate metal component and the non-metalpowder component. The exact proportions of the two major componentswill, of course, depend on the specific formulation and the amount ofmetal needed. In the typical example aforedescribed, if one blends about98.5 parts by weight of the non-metal powder component with about 1.5parts by weight of the coated aluminum, a "low metallic" automotivetopcoat paint results.

Appearance of the finished coating will, of course, be a primary factorin selecting the total concentration of aluminum flakes in the totalpowder paint composition. This concentration will vary from a very lowweight percent of the total powder paint composition in somepolychromatic finishes, i.e., as low as about 0.005 weight percent, to amuch higher weight percent of the total powder paint composition in theso-called "Argent" finishes, i.e., as high as about 25 weight percent.If for example, the spray dried coating on the flakes comprises about 2to about 30 weight percent by weight of the flakes, then the coatedflakes will comprise between about 0.005 to about 32.5, advantageouslybetween about 0.25 to about 28.75, and preferably between about 0.54 toabout 28.25, weight percent of the total powder paint composition. Theprincipal film-forming powder and non-metal pigment, if any, will makeup the balance of the powder paint composition. When metal flakes areused, the non-metal pigment will constitute between 0 and about 22weight percent of the total composition.

This method provides the additional advantage that the thin layer ororganic coating on the aluminum flakes substantially reduces the dangerof explosions which exists with dry aluminum flakes and the usualhandling of dry aluminum under inert gas atmosphere is not required.

This invention will be more fully understood from the followingillustrative examples.

EXAMPLE 1 a. Preparation of the Coated Aluminum Flakes

A powder paint in accordance with this invention is prepared from thefollowing material using the procedures hereinafter outlined:

1. Preparation of an epoxy-functional acrylic copolymer of vinylmonomers is prepared as follows:Ingredients Parts ByWeight______________________________________glycidyl methacrylate15methyl methacrylate 45butyl methacrylate40______________________________________

The above named ingredients are mixed together. Three (3) parts byweight of 2,2' - axobis - (2-methyl-propionitrile), hereinafter calledAIBN, is dissolved in the monomer mixture. The mixture is slowly addedto refluxing toluene (100 parts) which is stirred vigorously under anitrogen atmosphere. A condenser is provided at the top of the toluenecontainer to condense the toluene vapors and return them to thecontainer. The monomer mixture is added through a regulating valve andthe rate of addition is controlled to maintain a reflux temperature(109°C. - 112°C.) with only a small fraction of heat supplied from anexternal heater. After the addition of the monomer mixture is complete,the refluxing is maintained by external heat source for 3 additionalhours.

The solution is poured into shallow stainless steel trays. These traysare placed in a vacuum oven and the solvent evaporated therefrom. As thesolvent is removed, the copolymer solution becomes more concentrated.The temperature of the vacuum oven is raised to about 110°C. Drying iscontinued until the solvent content of the copolymer is below 3 percent.The trays are cooled and the copolymer collected and ground to passthrough 20 mesh screen. The copolymer has a glass transition temperatureof 53°C. and a molecular weight (M_(n)) of 4000.

One hundred parts by weight of the ground copolymer are mixed with thefollowing materials:azelaic acid 10.0 partspoly (lauryl acrylate) (M_(n)=10,000) 0.7 parts

The materials are mixed together in a ball mill for 2 hours. The mixtureis mill rolled at 85°C. to 90°C. for 5 minutes. The solid obtained isground in a ball mill and the powder is sieved with a 140 mesh screen.

Two (2) parts by weight of this thermosettable mixture are combined with30 parts by weight of aluminum paste (35 percent by weight mineralspirits and 65 percent by weight aluminum flakes that will pass througha 325 mesh screen and have typical surface area of 7.5 m² /g, maximumparticle diameter below 45 microns and most common particle sizedistribution in the range of about 7 to about 15 microns) and 200 partsby weight of methylene chloride under low shear agitation so as todisperse the aluminum in the thermosettable material without damage tothe aluminum flakes.

Once the above dispersion has been prepared, it is spray dried in amanner which will produce individual aluminum flakes coated with a thin,continuous coating of dry copolymer. This is accomplished in a 3 footdiameter spray drier equipped with a two-fluid nozzle in counter-currentposition using the following conditions:

    air flow in drying chamber                                                                        200 cubic feet/minute                                     feed rate of mixture                                                                              380 ml/minute                                             inlet air temperature                                                                             180°F.                                             two fluid atomization air pressure                                                                 80 lbs.                                              

The product obtained from this process has an overall composition of19.5 parts by weight of aluminum and 2.0 parts by weight of thethermosettable mixture aforedescribed plus a small amount of residualsolvent (i.e., 0.05 to 0.2 parts) that has not completely volatilizedduring the spray dry process. This product is then screened through a 44micron screen.

b. Preparation of the Non-Metal Powder Component

A thermosettable material is produced by mixing 166 parts by weight ofthe epoxy-functional copolymer employed in the thermosettable materialused to coat the aluminum flakes in (a) above with the followingmaterials:

                       Parts By Weight                                            ______________________________________                                        azelaic acid         22.65                                                    poly (lauryl acrylate)                                                                             1.34                                                     phthalo green pigment                                                                              1.75                                                     yellow iron oxide pigment                                                                          8.26                                                     ______________________________________                                    

A homogeneous mixture of the above is obtained by ball milling for 2hours. This mixture is then extruded at 100°C. from a kneading extruder.The solid thus obtained is pulverized in an impact mill, i.e., an airclassified impact mill, and sieved through a 200 mesh screen.

c. Preparation of the Powder Coating Material

A powder coating material in accordance with this invention is producedby mixing 1.65 parts by weight of the coated aluminum with 98.35 partsof the non-metal powder component. A homogeneous mixture of the twocomponents is obtained by rapidly tumbling the material in a partiallyfilled container for 20 minutes under ambient room conditions, i.e.,65° - 75°F. In preparing the powder by this method, it will be obviousto those skilled in the art that actual mixing times will vary somewhatwith the size of container and mechanical action.

It will be noted that in this example the thermosettable material usedto coat the aluminum flakes and the thermosettable material used to formthe non-metal powder component are crosslinkable with each other.

The powder thus obtained is then sprayed on an electrically groundedsteel substrate with a conventional electrostatic powder spray gunoperating at about 50 KV charging voltage. After spraying, the coatedsubstrate is heated to about 350°F. for about 25 minutes. The coatingthus obtained has good gloss and metal particle orientation. It isresistant to weathering and suitable for automotive top coatapplication.

EXAMPLE 2

A powder coating material is prepared following the procedure of Example1 with the following differences: (1) The coated aluminum flakes areprepared from the following materials.

    ______________________________________                                                            Parts By Weight                                           ______________________________________                                        aluminum paste        30.000                                                   (65% aluminum flakes and                                                       35% mineral spirits)                                                        thermosettable mixture                                                                               0.218                                                   (same epoxy-functional copolymer                                               used in example 1 in amount as                                                .195 parts by weight and poly                                                (azelaic anhydride) .023 parts                                                by weight                                                                    poly (lauryl acrylate)                                                                               0.001                                                   (M.sub.n =10,000                                                             methylene chloride    197.000                                                 ______________________________________                                    

The product obtained after spray drying has a composition of 19.50 partsby weight aluminum, 0.218 parts by weight thermosettable material and0.001 parts by weight poly (lauryl acrylate).

The coated aluminum thus produced in the amount of 1.52 parts by weightis combined with 98.48 parts by weight of the non-metal powder componentof Example 1 to yield a powder of the following composition:

                       Parts By Weight                                            ______________________________________                                        aluminum (dry)       1.50                                                     thermosettable film-former                                                                         92.91                                                     (a)epoxy-functional co-                                                        polymer 81.74                                                                (b) azelaic acid 11.15                                                        (c)Poly(azelaic                                                                anhydride) 0.02                                                             poly (lauryl acrylate)                                                                             0.66                                                     phthalo green        0.99                                                     yellow iron oxide    3.93                                                     ______________________________________                                    

This powder coating material is electrodeposited upon a metal substrateand heat cured as in Example 1. The resulting coating demonstrates goodgloss, metallic orientation, and weathering resistance.

EXAMPLE 3

A powder coating material is prepared following the procedure of Example1 with the following differences:

1. The starting mixture for preparation of the coated aluminum flakes isof the following composition:

                         Parts By Weight                                          ______________________________________                                        aluminum paste         30.00                                                   (65% by weight aluminum and                                                    35% by weight mineral spirits)                                              thermosettable mixture 5.46                                                    (a) epoxy-functional copolymer                                                  of Example 1 - 4.88                                                         (b) poly (azelaic                                                               anhydride) - 0.58                                                          poly (lauryl acrylate) 0.03                                                   methylene chloride     250.00                                                 ______________________________________                                    

This material is mixed and spray dried as in Example 1 and in theresultant material flakes have coating about 2.5 times thicker than thatof the coated flakes of Example 1. The empirical composition of thespray dried product by weight is as follows:

                       Parts By Weight                                            ______________________________________                                        aluminum (dry)       19.5                                                     thermosettable material                                                                            5.46                                                      (a) epoxy copolymer of                                                          Example 1 -- 4.88                                                           (b) poly (azelaic                                                               anhydride) 0.58                                                            poly (lauryl acrylate)                                                                             0.03                                                     ______________________________________                                         (2). Since the amount of coating on the aluminum flakes is here large     enough to be a significant factor, it is taken into consideration when     formulating the non-metal powder component. Here, the non-metal powder     component is prepared by combining 166 parts by weight of the ground     epoxy-functional copolymer of Example 1 with the following:

                       Parts By Weight                                            ______________________________________                                        azelaic acid         22.64                                                    poly (lauryl acrylate)                                                                             1.33                                                     phthalo green pigment                                                                              1.80                                                     yellow iron oxide    8.23                                                     ______________________________________                                    

Subsequent processing of the non-metal powder component is the same asin Example 1. 3. In the blending of the coated metal component and thenon-metal powder component, the ratio of coated aluminum to non-metalpowder component is altered because of the thickness of coating on thealuminum flakes. The ratio here is 1.93 parts by weight of coatedaluminum with 98.08 parts by weight of the non-metal powder component.The resultant powder coating maintains the pigment level and has thefollowing composition:

                         Parts By Weight                                          ______________________________________                                        aluminum               1.50                                                   thermosettable material                                                                              92.93                                                   (a) epoxy-functional                                                           copolymer of Example 1 - 81.79                                               (b) azelaic acid - 11.10                                                      (c) poly (azeliac anhy-                                                         dride) -  0.04                                                             poly (lauryl acrylate) 0.65                                                   phthalo green pigment  1.50                                                   yellow iron oxide      3.42                                                   ______________________________________                                    

This material is mixed, screened, electrostatically sprayed on a sheetsubstrate, and heat cured as in Example 1. The finish obtained hasexcellent properties and its appearance is similar to the coatingsprepared in Example 1.

EXAMPLE 4

The procedure of Example 1 is repeated except for the differences:

1. The coating of the aluminum flakes is prepared from 30 parts byweight of the same aluminum paste used in Example 1 (19.5 parts byweight aluminum), and 4.7 parts by weight of the thermosettablematerial, i.e., epoxy-functional copolymer of Example 1 and azelaic acidin the proportions used in Example 1, 0.4 parts by weight tetrabutylammonium bromide, and .03 parts by weight poly (lauryl acrylate).

2. Following the procedure of Example 3, the non-metal powder componentis adjusted and employed in an amount with the coated aluminum flakes toprovide the powder coating material to be sprayed with the same level ofpigment loading as in such material in Example 1.

Resultant powder coating material is electrostatically sprayed upon asteel substrate and heat cured thereon as in Example 1 and the resultantfinish has similar appearance to that obtained in Example 1.

EXAMPLE 5

The procedure of Example 1 is repeated except for the differences:

1. The coating of the aluminum flakes is prepared from 30 parts byweight aluminum paste used in Example 1 (19.5 parts by weight aluminum)and 0.98 parts by weight of the thermosettable material, i.e.,epoxy-functional copolymer of Example 1 and azelaic acid in theproportions used in Example 1, 0.1 parts by weight tetrabutyl ammoniumbromide, and 0.005 parts by weight poly (lauryl acrylate).

2. Following the procedure of Example 3, the non-metal powder componentis adjusted and employed in an amount with the coated aluminum flakes toprovide the powder coating material to be sprayed with the same level ofpigment loading as in such material in Example 1.

The resultant powder coating material is electrostatically sprayed upona steel substrate and heat cured thereon as in Example 1 and theresultant finish has similar appearance to that obtained in Example 1.

EXAMPLE 6

The procedure of Example 1 is repeated except for the differences:

1. The coating of the aluminum flakes is prepared from 30 parts byweight of aluminum paste used in Example 1 (19.5 parts by weightaluminum) and from 2.93 parts by weight of the thermosettable material,i.e., epoxy-functional copolymer of Example 1 and azelaic acid in theproportions used in Example 1 and azelaic acid in the proportions usedin Example 1, 0.29 parts by weight tetrabutyl ammonium bromide, and 0.02parts by weight poly (lauryl acrylate).

2. Following the procedure of Example 3, the non-metal powder componentis adjusted and employed in an amount with the coated aluminum flakes toprovide the powder coating material to be sprayed with the same level ofpigment loading as in such material in Example 1.

The resultant powder coating material is electrostatically sprayed upona steel substrate and heat cured thereon as in Example 1 and theresultant finish has similar appearances to that obtained in Example 1.

EXAMPLE 7

The procedure of Example 1 is repeated except for the differences:

1. The coating of the aluminum flakes is prepared from 30 parts byweight of aluminum paste used in Example 1 (19.5 parts by weightaluminum) and 1.76 parts by weight of the thermosettable material, i.e.,epoxy-functional copolymer of Example 1 and azelaic acid in theproportions used in Example 1, 0.18 parts by weight tetrabutyl ammoniumbromide, and 0.01 parts by weight poly (lauryl acrylate).

2. Following the procedure of Example 3, the non-metal powder componentis adjusted and employed in an amount with the coated aluminum flakes toprovide the powder coating material to be sprayed with the same level ofpigment loading as in such material in Example 1.

The resultant powder coating material is electrostatically sprayed upona metal substrate and heat cured thereon as in Example 1 and theresultant finish has similar appearance to that obtained in Example 1.

EXAMPLE 8

The procedure of Example 1 is repeated except for the differences:

1. The coating of the aluminum flakes is prepared from 30 parts byweight of the aluminum paste used in Example 1 (19.5 parts by weightaluminum) and 2.54 parts by weight of the thermosettable material, i.e.,epoxy-functional copolymer of Example 1 and azelaic acid in theproportions used in Example 1, 0.25 parts by weight tetrabutyl ammoniumbromide, and 0.01 parts by weight poly (lauryl acrylate).

2. Following the procedure of Example 3, the non-metal powder componentis adjusted and employed in an amount with the coated aluminum flakes toprovide the powder coating material to be sprayed with the same level ofpigment loading as in such material in Example 1.

The resultant powder coating material is electrostatically sprayed upona metal substrate and heat cured thereon as in Example 1 and theresultant finish has similar appearance to that obtained in Example 1.

EXAMPLE 9

The procedure of Example 1 is repeated except for the differences:

1. The coating of the aluminum flakes is prepared from 30 parts byweight of the aluminum paste used in Example 1 (19.5 parts by weightaluminum) and 0.39 parts by weight of the thermosettable material, i.e.,epoxy-functional copolymer of Example 1 and azelaic acid in theproportions used in Example 1, 0.04 parts by weight tetrabutyl ammoniumbromide, and 0.002 parts by weight poly (lauryl acrylate).

2. Following the procedure of Example 3, the non-metal powder componentis adjusted and employed in an amount with the coated aluminum flakes toprovide the powder coating material to be sprayed with the same level ofpigment loading as in such material in Example 1.

The resultant coating material is electrostatically sprayed upon a metalsubstance and heat cured thereon as in Example 1 and the resultantfinish has similar appearance to that obtained in Example 1.

EXAMPLE 10

The procedure of Example 1 is repeated except for the difference that afunctionally equivalent amount of an epoxyfunctional andhydroxy-functional copolymer of vinyl monomers is substituted for theepoxy-functional copolymer of Example 1 and a functionally equivalentamount of poly (azelaic anhydride) is substituted for the azelaic acid.The epoxy-functional and hydroxy-functional copolymer used in thisexample is prepared from the below listed components in the mannerhereinafter described.

    ______________________________________                                                                  Percent by Weight                                   Reactants       Grams     Of Total Reactants                                  ______________________________________                                        glycidyl methacrylate                                                                         225.0     15                                                  hydroxyethyl methacrylate                                                                     75.0       5                                                  butyl methacrylate                                                                            600.0     40                                                  styrene         75.0       5                                                  methyl methacrylate                                                                           525.0     35                                                  ______________________________________                                    

The above mentioned monomers are admixed in the proportions above setforth and 70.0 grams (4.5 percent based on combined weights ofreactants) of 2,2' - azobis - (2 - methyl propionitrile), hereinaftercalled AIBN, are added to the monomer mixture. The solution is addeddropwise over a 3 hour period into 1500 ml. toluene at 100° - 108°C.under nitrogen atmosphere. Then 0.4 grams of AIBN dissolved in 10 ml. ofacetone are added over a 1/2 period and refluxing is continued for 2additional hours.

The toluene-polymer solution is diluted in 1500 ml. acetone andcoagulated in 16 liters of hexane. The white powder is dried in a vacuumoven at 55°C. for 24 hours. This copolymer has molecular weight -M_(w) - M_(n) = 6750/3400 and the molecular weight per epoxy group isabout 1068.

EXAMPLE 11

The procedure of Example 10 is repeated with the single difference thatabout 35 percent of the poly (azelaic anhydride) is replaced with afunctionally equivalent amount of 12 - hydroxy stearic acid.

EXAMPLE 12

The procedure of Example 1 is repeated except for the difference that afunctionally equivalent amount of an epoxyfunctional, amide-functionalcopolymer of vinyl monomers is substituted for the epoxy-functionalcopolymer of Example 1 and a functionally equivalent amount of acarboxy-terminated polymer is substituted for the azelaic acid. Theepoxyfunctional, amide-functional copolymer used in this example isprepared from the below listed components in the manner hereinafterdescribed:

                             Percent By Weight                                    Reactants       Grams    Of Total Reactants                                   ______________________________________                                        glycidyl methacrylate                                                                          45      15                                                   acrylamide       15       5                                                   butyl methacrylate                                                                            111      37                                                   methyl methacrylate                                                                           129      43                                                   ______________________________________                                    

The above mentioned monomers are admixed in the proportions above setforth and 11.0 grams of 2,2' - azobis - (2-methylpropionitrile),hereinafter called AIBN, are added to the mixture. The mixture is slowlyadded to 200 ml. of toluene heated to 80° - 90° C. which is beingstirred vigorously under a nitrogen atmosphere. A condenser is providedat the top of the toluene container to condense the toluene vapors andreturn the condensed toluene to the container. The monomer mixture isadded through a regulating valve and the rate of addition is controlledto maintain a reaction temperature of 90° - 110°C. with the rest of theheat supplied from an external heater. After the addition of the monomermixture is completed (3 hours), 0.8 grams of AIBN dissolved in 10 ml.acetone is added over a 1/2 hour period and refluxing is continued for 2additional hours.

The resultant toluene-polymer solution is diluted with 200 mls. acetoneand coagulated in 2 liters of hexane. The white powder is dried in thevacuum over at 55°C. for 24 hours. Its molecular weight is determined tobe M_(w) /M_(n) =6700/3200 and WPE (molecular weight per epoxide group)is about 1000.

The carboxy terminated polymer to be used as crosslinking agent isprepared from the following materials in the following manner: Fivehundred grams of a commercially available epoxy resin, Epon 1001,(epoxide equivalent 450 - 525, melting range 64° - 76°C. molecularweight average 900°C.), is charged into a 500 ml. stainless steel beakerhaving a heating mantle. The epoxy resin is heated to 110°C. As theepoxy resin is stirred, 194 grams of azelaic acid are added. After areaction time of 30 minutes, a homogeneous mixture is obtained. Themixture resin, only semi-reacted, is poured out into an aluminum pan andcooled. The solid mixture is pulverized to pass through a 100 meshscreen by use of a blender. The mixture resin is only semi-reactedbecause if fully reacted it could not be powdered. A portion of thecarboxy terminated polymer is weighed out for making a powder coatingcomposition of this invention.

EXAMPLE 13

The procedure of Example 1 is repeated except for the difference that afunctionally equivalent amount of a hydroxy-functional copolymer issubstituted for the epoxy-functional copolymer of Example 1 and afunctionally equivalent amount of hexamethoxy melamine is substitutedfor the azelaic acid.

The hydroxy-functional copolymer used in this example is prepared fromthe below listed components in the manner hereinafter described:

    Reactants            Parts By Weight                                          ______________________________________                                        2-hydroxyethyl methacrylate                                                                        15                                                       ethyl acrylate       25                                                       methyl methacrylate  60                                                       ______________________________________                                    

A one liter, four-necked flask which contains 150 ml. of toluene and 150ml. of methyl ethyl ketone is heated until the contents of the flask areat a refluxing temperature of 85°C. A mixture of the above listedmonomers and 4 parts by weight of 2,2' - azobis - (2 - methylpropionitrile), hereinafter called AIBN, in the total amount of 208grams is added in a dropwise fashion over a period of one and a halfhours to the reaction mixture which is maintained at 85°C. After themonomer addition is complete, 0.5 grams of AIBN (dissolved in 20 gramsof toluene) is added dropwise. The refluxing is continued for anadditional one-half hour to complete the polymerization.

The solution is poured into shallow stainless steel trays. These traysare placed in a vacuum oven and the solvent evaporated therefrom. As thesolvent is removed the copolymer becomes more concentrated. Thetemperature of the vacuum oven is raised to 110°C. Drying is continueduntil the solvent content of the copolymer is below 3 percent. The traysare cooled and the copolymer collected and ground to pass through a 20mesh screen.

EXAMPLE 14

The procedure of Example 1 is repeated except for the difference that afunctionally equivalent amount of a selfcrosslinking copolymer issubstituted for the epoxy-functional copolymer and the azelaic acid.

The self-crosslinking copolymer used in this example is prepared fromthe following listed components in the manner hereinafterdescribed:Reactants Grams______________________________________glycidylmethacrylate 30methacrylic acid 21methyl methacrylate 129butylmethacrylate 120______________________________________

The monomers above listed are mixed with 12 grams of an initiator, i.e.,t-butylperoxypivate. Three hundred grams of benzene is charged into aone liter flask which is equipped with a dropping funnel, condenser,stirrer, thermometer and nitrogen inlet. The monomer mixture is placedin the dropping funnel. The flask is heated to 80°C. and a refluxing ofthe solvent is achieved. While maintaining the reaction temperature at80°C., the monomer mixture is added in a dropwise fashion over a 2 hourperiod. After the addition is complete, the reaction is continued foranother 2 hours. The contents of the flask are then cooled to roomtemperature.

One hundred ml of the resultant solution are mixed with 0.3 grams ofpoly (2-ethylhexyl acrylate). The mixture is dispersed and then is driedin a vacuum oven at 70°C. The powder coating obtained is ground to passthrough a 200 mesh sieve.

EXAMPLE 15

The procedure of Example 1 is repeated except for the difference thatthe poly (lauryl acrylate) is replaced with an equivalent amount of poly(butyl acrylate) having (M_(n) =9000).

EXAMPLE 16

The procedure of Example 1 is repeated except for the difference thatthe poly (lauryl acrylate) is replaced with an equivalent amount of poly(isodedecyl methacrylate).

EXAMPLE 17

The procedure of Example 1 is repeated except for the difference thatthe poly (lauryl acrylate) is replaced with an equivalent amount ofpolyethylene glycol perfluoro octonoate (M_(n) =3400).

EXAMPLE 18

The procedure of Example 1 is repeated with the single difference thatthe coated aluminum flasks are mixed with the principal film-formingpowder in an amount such that they comprise 0.005 weight % of the totalpowder paint composition.

EXAMPLE 19

The procedure of Example 1 is repeated with the single difference thatthe coated aluminum flakes are mixed with the principal film-formingpowder in an amount such that they comprise 32.50 weight percent of thetotal powder paint composition.

EXAMPLE 20

The procedure of Example 1 is repeated with the single difference thatthe coated aluminum flakes are mixed with the principal film-formingpowder in an amount such that they comprise 0.25 weight percent of thetotal powder paint composition.

EXAMPLE 21

The procedure of Example 1 is repeated with the single difference thatthe coated aluminum flakes are mixed with the principal film-formingpowder in an amount such that they comprise 28.75 weight percent of thetotal powder paint composition.

EXAMPLE 22

The procedure of Example 1 is repeated with the single difference thatthe coated aluminum flakes are mixed with the principal film-formingpowder in an amount such that they comprise 0.54 weight percent of thetotal powder paint composition.

EXAMPLE 23

The procedure of Example 1 is repeated with the single difference thatthe coated aluminum flakes are mixed with the principal film-formingpowder in an amount such that they comprise 28.25 weight percent of thetotal powder paint composition.

EXAMPLE 24

The procedure of Example 1 is repeated with the difference that thecoated aluminum flakes are the sole metal-pigment used and theyconstitute 10 weight percent of the total powder paint composition. Inthis example, non-metal pigments are not used.

EXAMPLE 25

The procedure of Example 1 is repeated with the differences that thecoated aluminum flakes are the sole metal-pigment used and theyconstitute 1 weight percent of the total powder paint composition. Inthis example, the non-metal pigments constitute 21.9 weight percent ofthe total powder paint composition.

EXAMPLE 26

The procedure of Example 1 is repeated with the following compositionaldifferences. The coated aluminum flakes are mixed with the principalfilm-forming powder in an amount such that they comprise 32.5 weightpercent of the total powder paint composition and the principalfilm-forming powder contains, as the sole non-metal pigment, phthalogreen pigment in an amount such that it comprises 0.25 weight percent ofthe total powder paint composition.

EXAMPLE 27

The procedure of Example 1 is repeated with the following compositionaldifferences. The coated aluminum flakes are mixed with the principalfilm-forming powder in an amount such that they comprise 4.0 weightpercent of the total powder paint composition and the principalfilm-forming powder contains a mixture of metal-free pigments in anamount such that it comprises 22 weight percent of the total powderpaint composition. The mixture of metal-free pigments consistspredominantly of chrome yellow with flaventhron (yellow organic), rediron oxide and carbon black present from trace amounts to above oneweight percent.

EXAMPLE 28

The procedure of Example 1 is repeated with the following compositionaldifference: The coated aluminum flakes are mixed with the principalfilm-forming powder in an amount such that they comprise 0.5 weightpercent of the total powder paint composition.

EXAMPLE 29

The procedure of Example 1 is repeated except for the difference thatthe non-metal powder component with which the coated aluminum flakes ismixed in a thermoplastic powder prepared from the following materialsusing the procedure hereinafter described:

                       Parts By Weight                                            ______________________________________                                        poly (methyl methacrylate)                                                                         100                                                        M.sub.n = 40,000                                                            poly (lauryl methacrylate)                                                                          2                                                         M.sub.n = 120,000                                                           tetrabutylammonium bromide                                                                         0.5                                                      ______________________________________                                    

The above ingredients are mixed in a twin shell tumbling mixer for 10minutes and then mill rolled at 190°C. for 15 minutes. The blend iscooled and pulverized to pass through a 200 mesh screen.

The above materials in the amount of 188 parts by weight are mixed withthe yellow iron oxide pigment (8.26 parts by weight), the phthalo greenpigment (1.75 parts by weight) and the poly (lauryl acrylate) (1.34parts by weight).

A homogeneous mixture of the above is obtained by ball milling for 2hours. This mixture is extended at 100°C. from a kneading extruder. Thesolid thus obtained is pulverized in an impact mill, i.e., an airclassified impact mill, and sieved through a 200 mesh screen.

A variety of other thermoplastic powders which can be used with theencapsulated aluminum flakes are disclosed in U.S. Pat. No. 3,532,530which is incorporated herein by reference.

EXAMPLE 30

A series of powder paints, A-E are prepared from the following materialsin the manner hereinafter set forth and later electrostatically sprayedas in Example 1 for test purposes.

STEP I

The materials listed below are thoroughly mixed.

    __________________________________________________________________________                  A    B    C    D    E                                           __________________________________________________________________________                  PARTS BY WEIGHT                                                 __________________________________________________________________________    1.                                                                              aluminum paste                                                                (65% metal) 30.00                                                                              30.00                                                                              30.00                                                                              30.00                                                                              30.00                                       2.                                                                              thermosettable                                                                mixture     9.75 13.65                                                                              19.5 29.25                                                                              39.00                                         (a) resin*  8.58 12.01                                                                              17.16                                                                              25.74                                                                              34.32                                         (b) polyazelaic                                                                 anhydride 1.17 1.64 2.34 3.51 4.68                                            % based on                                                                    weight of alumi-                                                              num       50.00                                                                              70.00                                                                              100.00                                                                             150.00                                                                             200.00                                      3.                                                                              poly(lauryl acrylate)                                                                     0.06 0.08 0.12 0.18 0.23                                        4.                                                                              methylene chloride                                                                        250.00                                                                             250.00                                                                             250.00                                                                             250.00                                                                             250.00                                      __________________________________________________________________________     *epoxy-functional copolymer of Example 1.                                

STEP II

This mixture is then spray dried as in the preceding examples and aproduct comprising aluminum flakes encapsulated in a thermosettablemixture of resin and crosslinking agent is obtained wherein the relativeweights of the components are as follows:

    __________________________________________________________________________                  A    B    C    D    E                                           __________________________________________________________________________                  PARTS BY WEIGHT                                                 __________________________________________________________________________    1.                                                                              aluminum flakes                                                                           19.5 19.5 19.5 19.5 19.5                                        2.                                                                              thermosettable mixture                                                                    9.75 13.65                                                                              19.50                                                                              29.25                                                                              39.00                                       3.                                                                              poly(laurylacrylate)                                                                      0.06 0.08 0.12 0.18 0.23                                        __________________________________________________________________________

STEP III

These encapsulated aluminum flakes are sieved through a 44 micronscreen. All particles left on the screen are rejected.

STEP IV

A non-metallic powder mixture is made up by thoroughly mixing the belowlisted materials after which the mixture is pulverized and sievedthrough a 75 micron screen. All particles left on the screen arerejected.

    __________________________________________________________________________                  A     B     C     D     E                                       __________________________________________________________________________                  PARTS BY WEIGHT                                                 __________________________________________________________________________    1.                                                                              Resin*      166   166   166   166   166                                     2.                                                                              Azelaic acid                                                                              22.64 22.64 22.64 22.64 22.64                                   3.                                                                              Poly(lauryl                                                                   acrylate)   1.34  1.34  1.34  1.34  1.34                                    4.                                                                              Pigments                                                                       (a) thalo green                                                                          2.03  2.03  2.04  2.06  2.08                                       (b) yellow iron oxide                                                                    8.04  8.07  8.11  8.18  8.25                                    __________________________________________________________________________     *epoxy-functional copolymer of Example 1                                 

STEP V

An evenly mixed blend is formed from the encapsulated aluminum flakes ofStep III and the nonmetallic powder mixture of Step IV in the followingrelative proportions:

                  A     B     C     D     E                                       __________________________________________________________________________                  PARTS BY WEIGHT                                                 __________________________________________________________________________    1.                                                                              encapsulated aluminum                                                         flakes      2.255 2.256 3.009 3.764 4.518                                   2.                                                                              nonmetallic powder                                                                        97.745                                                                              97.444                                                                              96.991                                                                              96.236                                                                              95.482                                  __________________________________________________________________________

The relative concentrations of ingredients in each of these blends is asfollows:

    Ingredient           Parts by Weight                                          ______________________________________                                        aluminum             1.50                                                     thermosettable material                                                        (resin and crosslinker)                                                                           92.91                                                    poly(laurylacrylate) 0.66                                                     phthalo green        0.99                                                     yellow iron oxide    3.93                                                     ______________________________________                                    

The powders thus obtained are sprayed on electrically groundedsubstrates and baked as in Example 1. Aluminum pigment spacing andorientation is best when the resin encapsulation on the aluminum flakesis in the range of 50 to 70 weight percent of the aluminum with the verybest achieved with paint A (50 weight percent encapsulation based on theweight of aluminum flakes).

EXAMPLE 31

Aluminum flakes are encapsulated as in Example 1 except for thedifferences that solvents other than methylene chloride, i.e., toluene,xylene, acetone, hexane and methyl ethyl ketone, are used to dispersethe film-forming material and aluminum flakes prior to spray drying. Thespray drying operation is adjusted in conformance with the relativevolalities of the solvent used in each test. The encapsulated flakesthus prepared are incorporated into the powder paint of Example 1,electrostatically sprayed upon substrates and the substrates are bakedas in Example 1.

Hydrocarbons alcohols, and ketones boiling in the range of 50°C. to152°C., preferably 50°C. to 90°C., can be used for this purpose. Theamount of solvent used is in excess of the combined weights of thealuminum flakes and the film-former used for encapsulation.Advantageously, the amount of solvent used is in the range of about 3 to100 times the combined weights of film-former and aluminum flakes.

Apparatus and methods for electrostatically spraying powder coatingmaterials are illustrated and described in U.S. Pat. Nos. 3,536,514;3,593,678; and 3,598,629.

The term "copolymer" is used herein to mean a polymer formed from two ormore different monomers.

Many modifications of the foregoing examples will be apparent to thoseskilled in the art in view of this specification. It is intended thatall such modifications which fall within the scope of this invention beincluded within the appended claims.

The disclosures of U.S. Pat. application Ser. No. 442,291 filed Feb. 12,1974 by Santokh S. Labana et al and entitled "Powder CoatingCompositions Including Glycidyl Ester-Modified Copolymer" areincorporated herein by reference.

Any and all disclosures appearing in the claims and not specificallyappearing in the body of this specification are herewith incorporated inthe body of this specification.

We claim:
 1. In a powder paint which exclusive of catalysts, antistaticagents, plasticizers, and flow control agents, the same being known andoptional additive to powder paints, consists essentially of aluminumflakes, non-metal pigment, and a particulate, organic, film-former, theimprovement whereinA. non-metal pigment comprises 0 to about 22 weightpercent of said powder paint, B. said aluminum flakes comprise about0.005 to about 24 weight percent of said powder paint and areencapsulated prior to admixture with said particulate, organic,film-former with about 2 to about 200 parts by weight of a continuouscoating of a thermosettable, organic, film-former per 100 parts byweight of aluminum flakes, said thermosettable, organic, film-formerconsisting essentially of a copolymer having average molecular weight(M_(n)) in the range of about 1500 to about 15,000 and glass transitiontemperature in the range of about 40°C. to about 90°C., bearingfunctional groups provided by constituent monomers selected from thegroup consisting of glycidyl esters of a monoethylenically unsaturatedcarboxylic acid, C₅ - C₇ monohydroxy acrylates, C₅ - C₇ monohydroxymethacrylates, and alpha-beta olefinically unsaturated amides andwherein at least above 50 weight percent of the constituent monomers areacrylic monomers and the remainder weight percent, if any, consistsessentially of C₈ -C₁₂ monovinyl hydrocarbons, said copolymer beingself-crosslinkable or employed in combination with a monomeric orpolymeric crosslinking agent that is capable of reacting with functionalgroups on said copolymer, and C. said particulate, organic, film-formeris selected from the group consisting of1. a thermoplastic, particulate,film-former having average molecular weight (M_(n)) in the range ofabout 30,000 to about 80,000 and a glass transition temperature in therange of about 60°C. to about 110°C., said thermoplastic, particulate,film-former being a polymer of alpha-beta olefinically unsaturatedmonomers of which about 51 to about 100 weight percent are acrylicmonomers and 0 to about 49 weight percent are C₈ -C₁₂ monovinylhydrocarbons, and
 2. thermosettable, particulate, film-formersconsisting essentially of a copolymer having average molecular weight(M_(n)) in the range of about 1500 to about 15,000 and glass transitiontemperature in the range of about 40°C. to about 90°C., bearingfunctional groups provided by constituent monomers selected from thegroup consisting of glycidyl esters of a monoethylenically unsaturatedcarboxylic acid, C₅ - C₇ monohydroxy acrylates, C₅ - C₇ monohydroxymethacrylates, and alpha-beta olefinically unsaturated amides andwherein at least above 50 weight percent of the constituent monomers areacrylic monomers and the remainder weight percent, if any, consistsessentially of C₈ -C₁₂ monovinyl hydrocarbons said copolymer beingself-crosslinkable or employed with a monomeric or polymericcrosslinking agent that is capable of reacting with functional groups onsaid copolymer.
 2. A powder paint in accordance with claim 1 whereinsaid powder paint also contains a flow control agent which comprisesbetween about 0.05 and about 4.0 weight percent of said powder paint andis a polymer having a molecular weight (M_(n)) of at least 1000, andhaving, at the baking temperature of the powder paint a lower surfacetension than the surface tension of said particulate, organic,film-former, and being a polymer or copolymer selected from the groupconsisting of acrylate esters, methacrylate esters, and polyethylene orpolypropylene glycol esters of fluorinated fatty acids, polymericsiloxanes, and polymeric halogenated siloxanes.
 3. A powder paint inaccordance with claim 1 wherein said aluminum flakes are encapsulated bydispersing 100 parts by weight of said aluminum flakes and about 10 toabout 200 parts by weight of said thermosettable, organic, film-formerin a volatile solvent boiling in the range of about 40°C to about 152°Cthat is fugitive from said thermosettable, organic, film-former and saidaluminum flakes in spray drying and spray drying said dispersion, saidsolvent being present in said dispersion in an amount in excess of thetotal amount of said aluminum flakes and said film-former.
 4. A powderpaint in accordance with claim 3 wherein said 100 parts by weight ofsaid aluminum flakes is dispersed in said solvent with 30 to 70 parts byweight of said thermosettable, organic, film-former, said solvent isselected from methylene chloride and alcohols, ketones and hydrocarbonsboiling in the range of about 40°C to about 90°C, and said solvent ispresent in said dispersion in an amount at least 3 times the combinedamounts of said aluminum flakes and said film-former.
 5. A powder paintin accordance with claim 1 wherein said encapsulation of said aluminumflakes is in the amount of about 30 to about 70 parts by weight of saidthermosettable, organic film-former per 100 parts by weight of saidaluminum flakes.
 6. A powder paint in accordance with claim 1 whereinsaid encapsulation of said aluminum flakes is in the amount of about 2to about 30 parts by weight of said thermosettable, organic film-formerper 100 parts by weight of said aluminum flakes.
 7. A powder paint inaccordance with claim 1 wherein said aluminum flakes are encapsulated ina thermosettable, organic, film-former consisting essentially of acopolymer of about 5 to about 20 weight percent of a glycidyl ester of amonoethylenically unsaturated carboxylic acid, about 2 to about 10weight percent of a hydroxy acrylate or methacrylate, and 70 to about 93weight percent of esters of a C₁ - C₈ monohydric alcohol with acrylic ormethacrylic acid and a crosslinking agent selected from the groupconsisting of dicarboxylic acids and anhydrides of dicarboxylic acids.8. A powder paint in accordance with claim 1 wherein said aluminumflakes are encapsulated in a thermosettable, organic, film-formerconsisting essentially of a copolymer of about 5 to about 20 weightpercent of a glycidyl ester of a monoethylenically unsaturatedcarboxylic acid, about 2 to about 10 weight percent of an alpha-betaolefinically unsaturated amide, and 70 to about 93 weight percent ofesters of a C₁ - C₈ monohydric alcohol and acrylic or methacrylic acidand a crosslinking agent selected from the group consisting ofdicarboxylic acids and anhydrides of dicarboxylic acids.
 9. A powderpaint in accordance with claim 1 wherein said copolymer of saidparticulate, organic, film-former is an epoxy-functional copolymer andis employed with a crosslinking agent selected from the group consistingof dicarboxylic acids and anhydrides of dicarboxylic acids.
 10. A powderpaint in accordance with claim 1 wherein said aluminum flakes areencapsulated in a thermosettable, organic, film-former consistingessentially of a copolymer of about 5 to about 20 weight percent of aglycidyl ester of a monoethylenically unsaturated carboxylic acid andabout 80 to about 95 weight percent of esters of a C₁ - C₈ monohydricalcohol and acrylic or methacrylic acid and a crosslinking agentselected from the group consisting of dicarboxylic acids and anhydridesof dicarboxylic acids.
 11. A powder paint in accordance with claim 8wherein said alpha-beta olefinically unsaturated amide is selected fromthe group consisting of acrylamide and methacrylamide.
 12. A powderpaint in accordance with claim 1 wherein said particulate, organic,film-former consists essentially of a copolymer of about 5 to about 20weight percent of a glycidyl ester of a monoethylenically unsaturatedcarboxylic acid and about 80 to about 95 weight percent of esters of aC₁ - C₈ monohydric alcohol and acrylic or methacrylic acid and acrosslinking agent selected from the group consisting of dicarboxylicacids and anhydrides of dicarboxylic acids.
 13. A powder paint inaccordance with claim 1 wherein said particulate, organic, film-formerconsists essentially of a copolymer of about 5 to about 20 weightpercent of a glycidyl ester of a monoethylenically unsaturatedcarboxylic acid, about 2 to about 10 weight percent of an alpha-betaolefinically unsaturated amide, and about 70 to about 93 weight percentof esters of a C₁ - C₈ monohydric alcohol and acrylic or methacrylicacid and a crosslinking agent selected from the group consisting ofdicarboxylic acid and anhydrides of dicarboxylic acids.
 14. A powderpaint in accordance with claim 1 wherein said particulate, organic,film-former consists essentially of a copolymer of about 5 to about 20weight percent of a glycidyl ester of a monoethylenically unsaturatedcarboxylic acid, about 2 to about 10 weight percent of a hydroxyacrylate or methacrylate, and about 70 to about 93 weight percent ofesters of a C₁ - C₈ monohydric alcohol and acrylic or methacrylic acidand a crosslinking agent selected from the group consisting ofdicarboxylic acids and anhydrides.